Spectral Tomography of Ultra-Cool Dwarf Radio Magnetospheres

超冷矮星射电磁层的光谱断层扫描

• 批准号: 1517412
• 负责人: Robert Mutel
• 金额: $ 37.21万
• 依托单位: University of Iowa
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-01 至 2019-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1517412&HistoricalAwards=false
• 关键词: Spectral; Tomography; Ultra; Cool; Dwarf

The primary scientific goal of the project is to determine the structure of magnetic fields in very low-mass stars. This study will broaden our understanding of how magnetic fields are generated in stars, which is currently not well understood. This could also contribute to our understanding of the Sun's magnetic field, which plays a key role in the potentially damaging solar magnetic storms that reach Earth during periods of high solar activity. The program will provide a graduate training opportunity for a student from a group that is underrepresented in astronomy. Results from this program will be integrated into a new undergraduate course being developed by the PI.This proposal addresses a fundamental question in stellar astrophysics: What is the nature of the surprisingly strong coronal magnetic fields in very low-mass stars? The research program comprises two parts. The first is an observational program to determine the dynamical spectra of a selected sample of ultra-cool dwarf stars that exhibit pulsed radio emission. The observations will utilize the Very Large Array to obtain wideband spectra over several epochs to establish the stability of the pulse periods, polarization, and morphology. The second part is the development of a realistic magnetospheric model that will be used to create synthesized wideband spectra. The model will include several plasma physics effects that have not been previously considered, such as cold-plasma ray tracing and angular beaming caused by density-depleted cavities. This scheme, denoted spectral tomography, will compare synthetic dynamic spectra with observations to constrain the geometry and plasma properties of the stellar magnetospheres.

该项目的主要科学目标是确定极低质量恒星的磁场结构。这项研究将拓宽我们对恒星中磁场是如何产生的理解，这一点目前还不太清楚。这也有助于我们了解太阳的磁场，它在太阳活动高峰期到达地球的潜在破坏性太阳磁暴中起着关键作用。 该计划将为来自天文学代表性不足的群体的学生提供研究生培训机会。 这个项目的结果将被整合到PI正在开发的一个新的本科课程中。这个提议解决了恒星天体物理学中的一个基本问题：在非常低质量的恒星中，令人惊讶的强大日冕磁场的性质是什么？研究计划包括两个部分。第一个是一个观测计划，以确定一个选定的样本的超冷矮星，表现出脉冲无线电发射的动态光谱。观测将利用甚大阵列获得几个时期的宽带光谱，以确定脉冲周期、极化和形态的稳定性。第二部分是发展一个现实的磁层模型，将用于创建合成宽带光谱。该模型将包括一些以前没有考虑过的等离子体物理效应，如冷等离子体射线跟踪和密度耗尽腔引起的角光束。这个计划，表示光谱层析成像，将比较合成的动态光谱与观测，以约束恒星磁层的几何形状和等离子体特性。